A powered device may be connectable to a power source during its operation such that a source voltage is suppliable to electronic components of the powered device. In a case in which a value of the source voltage for the powered device is higher than a value of the maximum allowable supply voltage for the electronic components, the powered device comprises a power limiting device configured for limiting, particularly down converting, the value of the source voltage to the value below the maximum allowable supply voltage for the electronic components of the powered device.
For example, such a powered device may be a Long Term Evolution (LTE)-Universal Serial Bus (USB)-modem and may be connectable to a personal computer comprising the power source for the modem. A connection between the modem and the power source may be accomplished via a USB socket-plug-connection during a time in which the modem comprises its operative state. The value of the source voltage may be set according to the USB standard of the personal computer, and may be between 4.75 Volt (V) and 5.25 V. Further, the electronic components of the modem may comprise a base band chip configured for communicatively coupling the powered device with a respective communications network. The base band chip may comprise a value of a maximum allowable supply voltage between 3.0 V and 4.6 V. Accordingly, the modem comprises a power limiting device configured as a buck regulator which is configured for down converting the value of the source voltage to the value below the maximum allowable supply voltage for the base band chip.
Usually, such a powered device may be optimized towards its required source voltage when being operative, in order to save energy for reasons of environmental protection. In particular, in a case in which the power source is configured as or may be comprised in a battery operated device (for example a mobile phone, a personal computer, a laptop, a tablet, a netbook, etc.), optimizing the powered device towards its required source voltage may help to minimize an amount of recharging cycles of the battery of the battery operated device.
Referring to the above described example, a power consumption of the modem may be subject to regulations both for its working state and its standby state. In the case of the above described LTE-USB-modem, an overall power consumption of the modem being in its standby state shall be as low as possible. Further, the USB specification may limit the overall power consumption to a certain value, for example, at most 2.5 milliampere (mA) for a USB 2.0 standard.
However, in the standby state of the modem, the internal power consumption of the buck regulator is already between about 10 mA and about 30 mA. The particular value of the power consumption of the buck regulator depends on an internal architecture of the buck regulator which may differ between different vendors of the buck regulator. The above stated values of the internal power consumption of buck regulator do not account for a required additional supply current for the load being in its standby state, which supply current has to be supplied by the buck-regulator as well. Accordingly, theses power consumption values are incompatible with the desired (overall) power consumption of the modem of about 2.5 mA.